Preparation of porous electrodes

Abstract

Electrodes with porous coatings are produced using an inorganic compound which is soluble in an aqueous solution, as the pore former in the coating. The inorganic pore former may be removed from the coating while the electrode is being used in an electrolytic cell without contaminating the electrolyte. Such electrodes are particularly useful in electrolytic cells, wherein they operate at a significantly lower voltage and have a longer life span than conventional electrodes.

We claim: 
     
       1. An improvement in the process for preparing electrodes having a porous coating including the steps of (a) coating an electroconductive electrode substrate with an admixture of: (1) an electroconductive metal; and   (2) a pore former; and     (b) removing the pore former from the electrode coating, wherein the improvement consists of removing the pore former while the electrode is in use in an electrolytic cell.     
     
     
       2. The process of electrolyzing an electrolyte in an electrolytic cell wherein: (1) the electrode is coated with an admixture of an electroconductive metal and an inorganic compound; wherein said inorganic compound is selected so that it is the same salt that is contained in the electrolyte;   (2) the electrode is placed in use in the electrolytic cell; and   (3) the inorganic compound is leached by the electrolyte, leaving a porous coating on the electroconductive metal.   
     
     
       3. The process of claim 2 wherein the electrolyte is an aqueous solution of a metal salt. 
     
     
       4. The process of claim 2 wherein the electrolyte is an aqueous solution of an alkali metal halide. 
     
     
       5. The process of claim 2 wherein the coated electrode is used as a cathode. 
     
     
       6. The process of preparing electrodes having a porous coating comprising the steps of: (a) coating an electroconductive electrode substrate, using plasma spraying techniques, with an admixture of (i) an electroconductive metal; and   (ii) an inorganic compound which is soluble in an aqueous solution; and     (b) removing the inorganic compound from the electrode coating.   
     
     
       7. The process of preparing electrodes having a porous coating comprising the steps of: (a) coating an electroconductive electrode substrate, using flame spraying techniques, with an admixture of: (i) an electroconductive metal; and   (ii) an inorganic compound which is soluble in an aqueous solution; and     (b) removing the inorganic compound from the electrode coating.   
     
     
       8. The process of preparing electrodes having a porous coating comprising the steps of: (a) coating an electroconductive electrode susbstrate with an admixture of: (1) electroconductive metallic compound, which is composed of at least one element selected from the group consisting of the elements listed in Groups I-B, V-B, VI-B, VII-B and VIII of the Mendeleev Periodic Table and at least one other element which is selected from the group consisting of one or more of the elements in the class consisting of boron, carbon, nitrogen, silicon, phosphorous, sulfur, arsenic, selenium and tellurium; and   (2) an inorganic compound soluble in an aqueous solution; and     (b) removing the inorganic compound from the electrode coating.   
     
     
       9. The process of preparing electrodes having a porous coating comprising the steps of: (a) coating an electroconductive electrode substrate with an admixture of: (1) an electroconductive metal; and   (2) an inorganic oxide soluble in an aqueous solution; and     (b) removing the inorganic oxide from the electrode coating.   
     
     
       10. The process of preparing electrodes having a porous coating comprising the steps of: (a) coating an electroconductive electrode substrate with an admixture of: (1) an electroconductive metal; and   (2) an inorganic sulfide soluble in an aqueous solution; and     (b) removing the inorganic sulfide from the electrode coating.   
     
     
       11. The process of preparing electrodes having a porous coating comprising the steps of: (a) coating an electroconductive electrode substrate with an admixture of: (1) an electroconductive metal; and   (2) an inorganic compound soluble in an aqueous solution; and     (b) removing the inorganic compound from the electrode coating while the electrode is in use in an electrolytic cell.   
     
     
       12. An improvement in the process for preparing electrodes having a porous coating including the steps of: (a) coating an electroconductive electrode substrate with an admixture of: (1) an electroconductive metal; and   (2) a pore former; and     (b) removing the pore former from the electrode coating, wherein the improvement consists of using, as the pore former, an inorganic compound which is soluble in an aqueous solution and is selected to match the composition of an electrolyte which is to be used in an electrolytic cell, so that no contamination of the electrolyte occurs when the inorganic compound is leached by the electrolyte.   
     
     
       13. The product produced by the process of claims 1, 2, 6, 7, 9, 10, 11 or 12.